Field of the Invention
The present invention relates to a liquid ejection head and a production process thereof, and particularly to a liquid ejection head provided with a sealant covering a lead wire and a production process thereof.
Description of the Related Art
A liquid ejection head has been utilized for various office equipment such as a printer and a copying machine in recent years and is going to spread rapidly to an industrial system such as a textile printing apparatus. Examples of a form of the liquid ejection head include such a form that separately and detachably installs a liquid ejection portion and a liquid tank and such a cartridge form that a liquid ejection portion and a liquid container are integrally formed.
FIG. 6 is a perspective view of a relevant liquid ejection head. As illustrated in FIG. 6, a liquid ejection head 1 is provided with an element substrate 2, an electrical wiring substrate 3 electrically connected to the element substrate 2 through a lead wire and a support member 4 supporting the element substrate 2 and the electrical wiring substrate 3. The lead wire is covered with a sealant 5.
As a process for producing the liquid ejection head 1 illustrated in FIG. 6, a production process including a step of filling two different liquid fillers around the lead wire to cure the fillers is proposed (Japanese Patent Application Laid-Open No. 2001-130001). The two different fillers are cured, thereby forming the sealant 5 covering a joint portion.
The production process disclosed in Japanese Patent Application Laid-Open No. 2001-130001 is described in more detail with reference to FIGS. 7A to 7D. FIGS. 7A to 7D are drawings for explaining the production process disclosed in Japanese Patent Application Laid-Open No. 2001-130001 and enlarged sectional views taken along line 7-7 in FIG. 6 and illustrating the element substrate 2, the electrical wiring substrate 3 and the support member 4.
As illustrated in FIG. 7A, a worker or a production apparatus first applies a mount adhesive 6 for fixing the element substrate 2 and a TAB-sticking adhesive 7 for fixing the electrical wiring substrate 3 to the support member 4. The worker or the production apparatus also electrically connects the element substrate 2 to the electrical wiring substrate 3 through the lead wire 8.
As illustrated in FIG. 7B, the worker or the production apparatus then arranges the element substrate 2 and the electrical wiring element 3 on the support member 4. At this time, a filler reservoir portion 9 is formed around the element substrate 2, and the lead wire 8 is arranged over the filler reservoir portion 9. Thereafter, the worker or the production apparatus pours a first filler 10 into the filler reservoir portion 9.
The first filler 10 is a thermally curable resin such as an underfilling material for flip chip that is used in bare chip mounting. The viscosity of the underfilling material is about 50 poises at ordinary temperature, but is 15 poises or lower at 40° C. to 70° C. That is, the viscosity of the first filler 10 is relatively low in a state of 40° C. to 70° C., and so the flowability thereof is relatively high.
The temperature of the support member 4 is kept to a temperature of 40° C. to 70° C. when the first filler 10 is poured into the filler reservoir portion 9, whereby the first filler 10 is kept to such a state that the flowability thereof is relatively high. The support member 4 is left to stand for about 3 to 10 minutes at the temperature of 40° C. to 70° C., whereby the first filler 10 spreads all over the filler reservoir portion 9 to reach the lead wire 8 (see FIG. 7C).
Thereafter, the worker or the production apparatus applies a second filler 11 on to the first filler 10. The second filler 11 is a thermally curable resin that has almost the same composition as the first filler 10, but has a higher viscosity and lower flowability than the first filler 10. Accordingly, the second filler 11 rises on the first filler 10, and the lead wire 8 is covered with the first and second fillers 10 and 11. Heat is applied to the first and second fillers 10 and 11, whereby the first and second fillers 10 and 11 are cured to form the sealant 5 covering the lead wire 8 (see FIG. 6).
In order to further reduce the production cost of the liquid ejection head, it is required to shorten the production time of the liquid ejection head and to simplify the work upon the production of the liquid ejection head. However, it has been difficult for the production process disclosed in Japanese Patent Application Laid-Open No. 2001-130001 to shorten the production time and to simplify the work upon the production.
Specifically, when the leaving time of the support member 4 after the first filler 10 is poured into the filler reservoir 9 is insufficient in the production process disclosed in Japanese Patent Application Laid-Open No. 2001-130001, a bubble 12 may become mixed in the first filler 10 as illustrated in FIG. 8. The bubble 12 rapidly expands when the first and second fillers 10 and 11 are cured by heating. As a result, the first and second fillers 10 and 11 splash to expose the lead wire 8. For this reason, the support member 4 needs to be left to stand for about 3 to 10 minutes after the first filler 10 is poured into the filler reservoir 9 to prevent the bubble from being mixed in the first filler 10, so that it has been difficult to shorten the production time.
In addition, the production process disclosed in Japanese Patent Application Laid-Open No. 2001-130001 has to use the two different fillers 10 and 11. Accordingly, the management of materials upon the production of the liquid ejection head is complicated, so that it has been difficult to simplify the work upon the production of the liquid ejection head.